Crude venom and at least six highly purified toxic fractions from the scorpion centruoides sculpturatus will be further studied on isolated nerve and nerve-muscle preparations, and on in vivo nerve-muscle preparations using appropriate electrophysiological and computer assisted measurement techniques. Transmembrane potential phenomena as well as twitch tension will be recorded and analyzed. Scorpion venom action appears to be modulated by divalent ions (Ca ions and Mg ions) and by other pharmacologic reagents (eg the phenothiazines). Experiments are designed to explore more completely venom and venom fraction effects with these reagents. It appears possible to define therapeutic protocol to control venom effects. Already initiated light and electron microscopic studies on frog nerve-muscle preparations will be continued. Possible ultrastructural changes induced by the venom will be documented.